1. Field of the Invention
This invention relates generally to a variably controlled microwave source, and more particularly, to a W-band variably controlled microwave source incorporating solid state diode oscillators exhibiting a stable frequency output.
2. Background of the Related Art
There are many applications known which require an RF source for the generation of a microwave output signal. Typical applications include tunable local oscillators, phase lock sources, transmitter drivers and signal generators. Many of these applications require a highly stable and compact microwave source which has low power losses. It has been known in the art heretofore to incorporate semiconductor oscillators as a compact source to generate the microwaves. Generally, these semiconductor oscillators will include at least one negative-resistance semiconductor. One popular negative-resistance semiconductor oscillator is the well known Gunn diode. A Gunn diode is a transfer electron-type device which achieves negative-resistance due to a transfer of electrons from high to low mobility in the energy bands of the semiconductor material. Other diodes, including avalanche diodes, tunnel diodes, etc., are also well known semiconductor oscillators.
In operation, a semiconductor oscillator will generate a microwave signal depending on the bias voltage which is applied to it. The semiconductor oscillator will generally resonate inside a waveguide chamber which amplifies the microwave frequency and directs it. Altering the chamber parameters effects the resonating frequency of the semiconductor source. In order to achieve fine-tuning of the output microwave, it is known in the art to utilize a varactor diode. A varactor diode is a passive P/N junction diode which has a variable capacitance as different bias voltages are applied to it. Consequently, if a bias voltage applied to a varactor diode is changed, the varactor diode will exhibit a change in its capacitance. Therefore, by capacitively coupling a varactor diode to a Gunn diode in the same waveguide chamber and altering the bias voltage applied to the varactor diode, the output of the microwave device can be tuned to a range of frequencies around the main frequency of the Gunn diode.
Many different variations and designs of the above described RF source are known in the art. However, these known devices generally do not achieve the most desirable frequency stability and low power losses required for the output frequency of a compact semiconductor source. Adverse environmental conditions causing vibration and temperature variations within the different components may effect the parameters of the microwave source causing undesirable shifts in the frequency output of the RF source. Clearly then, the less impact changes in the environment have on the different parameters of the microwave source, the greater the stability of the output signal.
What is needed then is a semiconductor microwave source which is reliable, dependable, compact and which does not suffer the drawbacks of the prior art as to adverse environmental conditions. It is therefore an object of the present invention to provide such an oscillator.